湘西北常页1井下寒武统牛蹄塘组页岩气聚集条件及含气特征

为评价湘西北地区下寒武统牛蹄塘组页岩气聚集条件及含气性，优选并实施钻探了湖南省第一口以牛蹄塘组为目的层段的页岩气参数井--常页1井，累计揭示了牛蹄塘组黑色页岩层系真厚度674.5 m，是目前中国单井钻遇的最大厚度黑色页岩层系。通过岩心样品有机地球化学、岩石矿物学、储层物性等实验分析，认为常页1井牛蹄塘组黑色页岩具有机碳含量高（平均为3.9%）、成熟度适中（等效R_o平均为2.6%）、脆性矿物含量高（石英含量平均为50.1%）、黏土矿物含量低（平均为32.4%）、低孔低渗（孔隙度、渗透率平均分别为1.7%、1.32×10^-3mD）、中小孔及裂缝发育的特征，具有良好的页岩气聚集条件。岩心现场解析实验和等温吸附实验都显示出常页1井具有良好的含气性，且整体上含气量随深度的增大而增加，其中井段1 100~1 250 m的黑色页岩段平均有机碳含量高达10.1%，现场解析总含气量为0.5~2.1 m³/t，等温吸附含气量为3.7~6.4 m³/t，是该井页岩气发育最有利的深度，显示出以常页1井为代表的湘西北牛蹄塘组具有良好的页岩气勘探开发潜力，鉴于其沉积厚度巨大，应优先对牛蹄塘组中下部黑色页岩进行勘探开发。

Shale gas accumulation conditions and gas-bearing properties of the Lower Cambrian Niutitang Formation in Well Changye 1, northwestern Hunan

This study evaluates shale gas accumulation conditions and gas-bearing properties of the Lower Cambrian Niutitang Formaion in northwestern Hunan, China. An optimal parameter well of shale gas in the Niutitang Formaion, Changye 1, was selected and drilled for the first time in Hunan Province. Collectively, it revealed the presence of dark shale series in the Niutitang Formation up to 674.5 m (true thickness), i.e., the thickest black shale series encountered during single-well drilling in China up to now. Core sampling and experimental analysis regarding organic geochemistry, rock mineralogy and reservoir properties show that the black shale of Niutitang Formation features high organic carbon content (average TOC content, 3.9 %), moderate organic maturity (equivalent Ro, 2.6 %), high brittle mineral content (quartz content, 50.1 %), low clay mineral content (average clay content, 32.4 %), poor porosity (1.7 %) and permeability (1.32×10^-3mD), and well-developed meso-/micropores and faults, which provide good conditions for shale gas accumulation in Well Changye 1. The well on-site desorption and isothermal adsorption tests show that the black shale of Niutitang Formation has good gas-bearing properties, with gas content generally increasing with depth. In Well Changye 1, the depth interval most favorable for shale gas accumulation is 1 100-1 250 m, as indicated by the average TOC content up to 10.1 % and the gas contents of 0.5-2.1 (well on-site desorption) and 3.7-6.4 m³/t (isothermal adsorption). The Niutitang Formation in northwestern Hunan, as represented by Well Changye 1, has good prospect for shale gas exploration. Considering its huge sedimentary thickness, the black shale of Niutitang Formation in the middle-lower part should be given priority for exploration.